help with welding glass

[woody12]

Hi, after seeing all the good efforts of people using welding glass a friend got me a piece of glass grade 10 he tells me. I used it but the result was terrible and wondered how others set up their camera. Do you set the camera to manual? Stuck the glass to ring adpater with no light getting through but the result was really dark and green. I know i can convert to black and white but even this made the result grainy and and unfocused. I'm using a nikon 3100. I don't expect miracles for this but the result was not worth the effort. Mindyou the weather was awful. Any help would be nice. Thanks

 

[big soft moose]

if the shot was really dark then your exposure wasnt long enough... the idea of welding glass, and indeed of ten stop filters generally, is to reduce the ammount of light getting in per second so that you can shoot really long exposures

the green is hard to deal with except by converting to B&W (which is why most people eventually splash out on a neutral ten stopper) but the noise showing up as grain is caused by your image being underexposed.

Settings wise meter for the scene normally without the 'filter' on and focus then switch to manual focus and M and then add ten stops to your exposure time and set that (remember that exposure is exponential so if the unfiltered exposure is 1/250 at f8 , then your filtered exposure should be 4 seconds at f8)

a bit of trial an error may be necessary as welding glass isnt set in specific stops

 

[rob-nikon]

+1 to the method above.

I've tried welding glass too, you can get very good results considering the very low cost. I found the 10 grade welding glass I used wasn't near a true 10 stop filter, it ranged from somewhere between 10-13 stops. This meant it extended the time range quite a bit. The example used above at 1/250 second it would need a shutter time ranging between 4-40 seconds, it's best to experiment a bit with the times, may explain your dark image. I've brought a bit of grade 8 welding glass off eBay (about £2 inc p&p) to see it that's nearer a 10 stop filter time. it looks lighter but I haven't had time to try it.

 

[HoppyUK]

Longer exposure, until you get it right. Grade 11 is a lot, probably around 12-15 stops. Usually a bit of trial and error is invloved, but once you know the exposure factor for your particular filter, it should stay constant. If it is as much as 15 stops, then that would make 1/1000sec into 32 seconds

Welding glass is not great on colour, but usually not bad and a custom white balance usually sorts it out reasonably well in-camera. Or sort it out in post processing. A mono conversion is a last resort really.

Massive thread on using welding glass here http://www.talkphotography.co.uk/forums/showthread.php?t=151141

 

[Just Dave]

Stuck the glass to ring adpater with no light getting through but the result was really dark and green. Thanks

i take a shot then use that as a custom white balance, that gets rid of the green cast, focus in AF then put in MF Before you hold the the glass in front of the lens, I find just holding it in front of the lens easier, as focus isnt affected

 

[woody12]

Thanks for all your help, makes a lot more sense now. Only trouble I have is that my shutter speed only goes to 30secs or am I missing something? How do I set my nikon to shot longer than this? Sorry this must sound really stupid to ask.

 

[big soft moose]

If you need to shoot longer than 30 secs get yourself a remote release and put the setting on Bulb (B) and time it by your watch

(it gos without saying that for any long exposure the camera needs to be on a tripod or other solid support)

[and this is 'talk basics' there's no such thing as a stupid question in here ]